Vindication may be an abstract concept, but it looks a little like this: five thousand delirious Brightonians of various hues and ages, hollering along to "Bonkers", Dizzee Rascal's appositely named No 1 hit. Pyrotechnics pop; confetti pirouettes through the air and Dizzee – possibly the happiest man to hail from the benighted borough of Bow, east London – grins goofily.

Ten years ago, the young Dylan Mills was an alienated teenager fashioning caustic home-made tracks for pirate radio. After a Mercury prize and modest success, he idled a little mid-decade. Now he has four UK No 1 hits to his name, a feat performed on his own independent label, Dirtee Stank. With crossover singles like "Dance wiv Me" and "Holiday", built with the help of dance producers such as Calvin Harris, Dizzee did what most believed could not be done. He turned grime (that dissonant UK hip-hop variant) into a commodity.

His audience is now a pop audience, and the boy in the corner is now a star, picking up a Brit for best British male last month. Others have followed into the charts – Tinie Tempah, Tinchy Stryder, Chipmunk and N-Dubz – creating a new strain of hegemonic urban pop. You might almost conclude that UK hip-hop has been completely assimilated by the pop machine, were it not for the cancellation of rising rapper Giggs's tour this week on police advice. It remains difficult for grime acts to play live in London, thanks to Form 969, a risk assessment pro forma for venues and promoters which appears actively to discriminate against urban music.

This kind of petty harrassment seems a distant memory tonight. Dizzee's Brighton date comes at the close of his post-Brits tour, one that is now morphing into a double-header with fellow Brit winner Lily Allen. Tonight, though, he has only his veteran DJ, Semtex, and Scope, his hype man, for company.

British hip-hop has always existed in a state of tension with its American cousin, the poor relation in terms of sales and cultural clout. But at the Brits, when Dizzee and Florence Welch wrapped up their glitter-strewn performance of "You Got the Dirtee Love" – the mashup of Welch's hit, "You've Got the Love" and Dizzee's own "Dirtee Cash", which has since gone to No 1 in the downloads chart – it did not compare unfavourably with Jay-Z and Alicia Keys's earlier rendition of "Empire State of Mind". It was impressive: glossy, gritty and further proof that grime could pay.

Welch might have been a welcome antidote to the unreconstructed attitude which dogs some of Dizzee's rhymes tonight. You become accustomed to a certain sexual frankness with hip-hop, but "Freaky Freaky" – one of many tracks tonight from Tongue N' Cheek – encourages people to point to girls in the audience who might be of a "freaky" disposition.

However much Dizzee captured the alienation of his generation with his early work, and however much his appeal now rests on his sense of fun, it would be refreshing if "the ladies" were treated with a little more imagination. There is some comedy value in another tune, though. Slow jams are traditionally romantic, but the only one tonight – "Chilling wiv My Mans Dem" – is an ode to playing computer games with his pals.

Dizzee's recent hits are clustered at the end of a gig lasting just over an hour. Compared with "Bonkers", which features a superb technoid assault fashioned by Armand Van Helden, "Dance wiv Me" and "Holiday" aren't exactly artistic achievements, but effective shoutalongs. When Dizzee is good, though, he whips up great blizzards of words as Semtex lets loose ear-blistering sounds. "Sirens" remains a terrific tune, tense and cacophonous, and "Fix Up Look Sharp" has lost none of its edge.

Dizzee's newfound status hasn't materially altered the way the rapper goes about his business. He still trades rhymes and loose-limbed old-school hip-hop dance moves with Scope at the start of "Pussyole (Old Skool)". There is less a costume change than a shirt swap, during a brief mid-set break in which the rapper presumably gets his worn-out tongue massaged for a few minutes. Having started the gig in a T-shirt with his own face on it, echoing graphic artist Shepard Fairey's iconic Obama "Hope" design, he ends it in a red basketball top. Wearing your own T-shirt might not be de rigueur in certain circles, but this is a demographic whose attitude to self-promotion is resolutely unprecious, and Dizzee is now an entrepreneur as well as an artist, keen to maximise branding opportunities. His Tongue N' Cheek album has a logo featuring the most visually arresting tongue since the Rolling Stones.

The main thing that hits you, though, is the bass. It's a monstrous, tactile thing, wafting like a nuclear breeze over your skin before curdling your ear wax. Dizzee may now be playing to 10-year-olds, but the frequencies coming off the stage are as fearsome as any at a proper rave in some insalubrious warehouse. Authenticity is a fraught topic in pop music, but Dizzee's massive low-end remains a welcome vestige of the old danger still just about shadowing Britain's new strain of pop.